An ongoing challenge in the development of prosthetic devices is the attachment of the prosthetic device to the residual limb of a user. For prosthetic legs, it is often difficult to securely attach the prosthetic leg to the residual leg without exerting too much or uneven pressure on the residual limb. On the one hand, the lack of a secure attachment can adversely affect the user's ability to walk. On the other hand, an improper fit can cause sores, swelling and pain for the user.
One approach for overcoming this challenge has been the application of a negative pressure vacuum in a space between the limb (or a liner donned on the limb) and a socket or receptacle coupled to the prosthetic limb. Two conventional ways to apply such a vacuum are by a mechanical pump or an electronic pump.
Mechanical pumps are often in-line systems that utilize the movement of the user to generate the negative pressure vacuum in the socket. For example, the force generated by contacting the ground during a user's walking motion can be used to generate a vacuum in the socket space to hold the prosthesis to the user's limb. However, in utilizing the motion of the user, known pumps rely on complete compression of the pump to expel air from the pump before the pump can be decompressed to generate the vacuum. Because the impact and displacement of the pump is not consistent and varies between users, the vacuum and thus attachment between residual limb and the socket can be unpredictable and/or inadequate, causing the user discomfort, grief and even injury.
Different attempts have been made to design a more efficient pump. For instance, U.S. Pat. No. 9,072,617 (commonly owned by assignee) describes a membrane pump system including a frame component and a support blade component, with a flexible membrane between them. The support blade component is attached to prosthetic foot near the ankle, while the frame component sits on a heel pad. The frame and support blade components are fixed to each other where they coincide close to the middle of the foot. The frame and blade components are designed so that when weight is placed on the heel of the prosthetic foot the frame component moves upward and the support blade components moves downwards, thus pulling and expanding the membrane between them. Accordingly, the membrane pump mechanism is located between the two frame components. When the membrane expands, air is efficiently drawn from the socket.
While the membrane pump system described in U.S. Pat. No. 9,072,617 tends to generate a more efficient vacuum, the frame and support blade components add bulk and weight to the prosthetic limb, imposing a greater burden on the user when walking. Furthermore, the arrangement of the frame and support blade components in relation to each other and the foot can affect the functionality of the foot. In addition, the membrane pump system must engage the heel of the prosthetic foot to generate a vacuum, limiting its versatility.
There is a need for a prosthetic device, system, and pump mechanism that provides freedom of vacuum suspension for a prosthetic system. There is also a call for a prosthetic device that provides a secure vacuum without losing suction and confidence to the user over a period of use. It is also desirable for prosthetic devices to draw a vacuum while being lightweight, streamlined, and versatile.